How Light Exposure Impacts Sleep: Morning, Evening and Everything In Between

Getting enough sleep is not just about when the lights go off. It also depends on when and how the lights come on. Our sleep-wake cycle is heavily influenced by light exposure. From sunrise to smartphone screens, the type and timing of light a person encounters plays a critical role in regulating their circadian rhythm.

Key Takeaway: Light exposure is one of the most powerful tools for resetting the body's internal clock. Misusing it can delay sleep and reduce sleep quality.

This blog explores how morning light boosts alertness and energy, how evening light disrupts sleep hormones, and what science says about the best light practices for better rest. Featuring insights from neuroscientist Dr Andrew Huberman and evidence from UK-based studies, we will break down how to use light to improve sleep, naturally and effectively.

Why Light Matters: A Quick Primer on Circadian Rhythms

The body runs on a 24 hour internal clock known as the circadian rhythm. This rhythm controls when a person feels alert and when they feel sleepy. Light, particularly sunlight, is the main signal that tells the brain what time of day it is.

When light enters the eyes in the morning, it activates photoreceptors in the retina that send signals to a region of the brain called the suprachiasmatic nucleus. This area sits in the hypothalamus and acts as the master clock. The suprachiasmatic nucleus then adjusts the timing of melatonin release, body temperature, alertness, and other bodily functions.

Insight from Andrew Huberman

Dr Andrew Huberman, a neuroscientist at Stanford University, has repeatedly highlighted the importance of getting natural light exposure early in the day. According to his guidance, receiving ten to thirty minutes of morning light within an hour of waking can significantly improve sleep later that night.

He also notes that artificial indoor lighting does not have the same biological impact as natural light. Even on a cloudy day in the UK, the intensity of natural light far exceeds indoor lighting in terms of lux and spectrum. This makes morning light one of the most powerful behavioural tools available to set the circadian rhythm correctly.

Morning Light: Your Body’s Natural Alarm Clock

Morning light exposure is the most important anchor for circadian rhythms. Light in the blue spectrum around 460 to 480 nanometres is especially effective in halting melatonin production and increasing alertness.

In the UK, even during winter months, natural daylight can still provide this benefit if people are intentional about stepping outside. Researchers have found that people who work near windows or spend time outside in the morning report better mood, productivity, and sleep efficiency at night.

Benefits of Morning Light

Receiving morning light exposure can:

• Help shut down melatonin production for better alertness

• Increase serotonin levels, which later help form melatonin at night

• Strengthen the timing and amplitude of the sleep-wake cycle

• Reduce the time it takes to fall asleep at night

Practical Tips

Aim to get outside for at least ten to thirty minutes within the first hour after waking. Do not wear sunglasses during this period unless necessary for medical reasons. If outdoor light is limited or you live in northern parts of the UK, consider using a medically certified light therapy box with at least ten thousand lux output.

Midday and Afternoon Light: Sustaining Wakefulness

Light during the midday and early afternoon is less effective at shifting the circadian rhythm, but it still plays a role in sustaining energy levels. It helps reinforce the body’s daytime alertness phase and prevents daytime sleepiness or dips in energy.

Some people who spend all day indoors under weak artificial lights may find themselves feeling drowsy in the afternoon yet unable to sleep at night. This flattening of the circadian curve can often be corrected by ensuring enough bright light exposure during the earlier parts of the day.

Try to eat lunch near a window or take a midday walk outdoors if possible. For office workers, sitting closer to windows or working under daylight spectrum bulbs can also help.

Evening Light: A Hidden Sleep Disruptor

As evening approaches, the body naturally begins to wind down by increasing melatonin production. This process is disrupted by artificial lighting, particularly from overhead LEDs and screens.

The problem is that modern light sources are heavily weighted toward the blue spectrum, which the brain interprets as daytime. This tricks the body into suppressing melatonin, delaying sleepiness and pushing the circadian rhythm later.

A 2011 study published in the Journal of Clinical Endocrinology and Metabolism found that even modest exposure to artificial room lighting during the evening significantly reduced melatonin secretion. In some cases, melatonin onset was delayed by over an hour.

Dr Huberman advises reducing exposure to overhead lighting in the evening and switching to low-level lamps with warm tones under three thousand kelvin. This change in light temperature and intensity can protect melatonin levels and ease the transition to sleep.

Screens and Sleep: A Modern Mismatch

Tablet screens emit concentrated blue light

Screens emit concentrated blue light directly into the eyes, making them uniquely disruptive to the brain’s understanding of time. Whether it is a television, tablet, or phone, using a screen in the hour or two before bed has been shown to:

• Delay melatonin onset by up to ninety minutes

• Reduce REM sleep proportion

• Increase the likelihood of waking during the night

• Lead to a sensation of non-restorative sleep in the morning

Even dimming the brightness of a phone does not eliminate the blue wavelength content. The most effective solution is to avoid screens entirely during the final ninety minutes before bed. If that is not feasible, consider using amber-tinted glasses that block blue light or installing software that shifts your device’s display to warmer tones.

The Impact of Light for Shift Workers

Shift workers face unique challenges because they must often stay awake and alert when their circadian biology is preparing for sleep. Bright light during the night and darkness during the day create conflicting signals, leading to sleep disorders, fatigue, and long-term health risks.

For those working overnight shifts, it is important to use bright artificial lighting in the workplace to support alertness. After work, wearing wraparound sunglasses on the commute home can help reduce unwanted light exposure. At home, creating a sleep environment that is completely dark using blackout curtains and eye masks can help support daytime sleep.

Some shift workers may also benefit from timed light therapy using high-lux lamps to create artificial dawn and dusk cues. This should be done under medical guidance for best results.

Creating a Daily Light Routine for Better Sleep

Understanding how light influences sleep allows people to use it intentionally throughout the day. Here is a general light hygiene schedule:

Morning:

Spend ten to thirty minutes outdoors without sunglasses as soon as possible after waking. Stand where your eyes can receive open sky light rather than staying in shade or facing a wall.

Afternoon:

Keep exposure to natural light high by working near windows or taking walks. Avoid spending the entire day in dark rooms or wearing heavily tinted lenses.

Evening:

Start dimming lights around two hours before bedtime. Use lamps instead of overhead bulbs. Switch to warm lighting and reduce screen time as much as possible.

Night:

Sleep in a room that is as dark as possible. Use blackout curtains and unplug any light-emitting devices. If total darkness is not an option, wear a well-fitted sleep mask.

Should You Invest in a Light Therapy Lamp?

Light therapy lamps can be an excellent investment for those who wake up before sunrise, live in dark climates, or struggle with seasonal mood changes. They are most effective when used in the morning shortly after waking.

Look for lamps that provide ten thousand lux at a comfortable distance and are medically certified for treating Seasonal Affective Disorder. Sit within arm’s reach of the lamp for fifteen to thirty minutes each day, ideally while eating breakfast or working.

Bryan Johnson - the famed biohacker - starts every day with immediate exposure to bright morning light (10,000 Lux) with a Carex lamp.

The Role of Light in Mental Health and Sleep

Light exposure does not just affect sleep. It also has profound effects on mental health. Morning light is associated with higher serotonin levels, better mood, and lower risk of depression. Conversely, disrupted circadian rhythms are linked with increased anxiety and poorer emotional regulation.

By aligning light exposure with the body’s natural rhythm, people can improve not only their sleep but their mental clarity, energy levels, and emotional wellbeing. This is especially important during the darker months in the UK, when light deprivation is common.

Conclusion: Light Is a Powerful Lever for Sleep

Many people focus on diet, exercise, and supplements to improve sleep. But light is often the missing piece of the puzzle. It sets the rhythm, governs hormone release, and controls the timing of sleep and wakefulness.

Whether it is going outside in the morning, avoiding screens at night, or using warm lamps in the evening, small adjustments to daily light exposure can make a major difference. These habits are simple, low-cost, and highly effective for supporting natural, restorative sleep.

As Dr Andrew Huberman and others have made clear, using light strategically may be one of the most underappreciated health habits of all.